Combination of relatively thin sheet of metal and pierce nut

ABSTRACT

A combined self-clinching pierce-type fastener and panel is disclosed wherein by a single stroke of a ram a threaded fastener, such as a nut, acts as a punch and pierces its own hole in the sheet metal panel to which it is to be fastened. The nut has one or more laterally extending flanges which abut upon one side of the said panel, the corners of the nut being displaced laterally in the die associated with the piercing operation, preferably under the flange, to clinch the material therebetween. The panel is also displaced at the displaced region of the nut and in the same general direction as the displaced region of the nut. The displaced material of the nut and panel is compressed together to form in the plane of the panel a circular convex boss.

United States Patent [191 [111 3,920,059 Grube [451 Nov. 1s, 1.975

[54] COMBINATION OF RELATIVELY THIN SHEET OF METAL AND PIERCE NUT [75]Inventor: William L. Grube, Lake Bluff, Ill. [73] Assignee: MacLean-FoggLock Nut Co.,

Mundelein, Ill.

[22] Filed: Jan. 17, 1974 [21] Appl. No.: 434,197

1 A Related US. Application Data [60] Continuation of Ser. No. 247,462,April 25, 1972, abandoned. which is a division of Ser. No. 13,007,

Feb. 20. 1970, Pat. No. 3,693,237.

[52] US. Cl, l5l/41.72 [51] Int. Cl. F16B 37/04 [58] Field of Search151/4172, 41.73

[56] References Cited UNITED STATES PATENTS 2,750,660 6/1956 Newcombl5l/41.72

Primary Examiner-Edward C. Allen [57 ABSTRACT A combined self-clinchingpierce-type fastener and panel is disclosed wherein by a single strokeof a ram a threaded fastener, such as a nut, acts as a punch and piercesits own hole in the sheet metal panel to which it is to be fastened. Thenut has one or more laterally extending flanges which abut upon one sideof the said panel, the comers of the nut being displaced laterally inthe die associated with the piercing operation, preferably under theflange, to clinch the material therebetween. The panel is also displacedat the displaced region of the nut and in the same general direction asthe displaced region of the nut. The displaced material of the nut andpanel is compressed together to form in the plane of the panel acircular convex boss.

3 Claims, 18 Drawing Figures U.S. Patent Nov. 18, 1975 Sheet 1 of23,920,059

US. Patent N0v.18, 1975 Sheet 2 0f2 3,920,059

COMBINATION OF RELATIVELY THIN SHEET OF METAL AND PIERCE NUT' I Thisapplication is a continuation of my co-pending application, Ser. No.247,462, filed Apr. 25, 1972 and now abandoned, which is a division ofapplication Ser. No. 13,007, filed Feb. 20, 1970., now us. Pat. No.3,693,237 for METHODOF SECURING FASTENER TO SHEET MATERIAL AND RESULTINGSTRUC- TURE.

This invention relates to a combination of a sheet of metal or the likewith a fastener secured theretoby deforming portions of thefastenerandmaterial. For purposes of illustration this invention will be describedwith reference to the application of pierce nuts to sheet metal,although. it is understood that it may be applied as well to securingother devices such as screws, bolts and pins to such sheet metal.

Self-piercing fasteners-are understood tobe fasteners which are used aspunches to form the opening in sheet metal through which theyare.toextend-andin which they are to be non-rotatively secured.. The,re areat present two general methods for piercing a sheet metal panel with afastener and securing the piercing fastener to the sheet. The first andmost widely used requires that the fastener be formedadjacent the noseor pilot part first entering the sheet metal, with a portion of thefastener reduced in cross-sectional ,area by undercutting, grooving orthe like. The sheet material adjacent the portion of reduced area isthen forced by acoining, swaging or die forming process, to movelaterally into the reduced area to form a lock between the fastener andsheet metal. This meth od requiresa predetermined strength and ductilityin the sheet material and a very critical adjustment of thefinalposition of the mechanism used to force the metal into the reducedarea. Too little force will result in an insufficient movement of thesheet material and a correspondingly weak interlock between the fastenerand material, and too much force will weaken the material itself.Furthermore; they formation of the reduced area-.in the fastenerisdifficult to 1 achieve on equipment designed for high volume productionof either cold or hot formedfasteners.

, The second method does not require a portion of reduced cross-sectionin thefastener, but nequiresinst ead that the pilot of the fast eneri.e;, the part of thefastener used as a punch to pierce the sheetmaterial, after sary interlock or clinch therewith. ,Severaldifficulties.

are inhereritin this method. One of these difficulties 'is that thedeformation can. only be accomplished by a.-

step in the back-up die which iscontacted by thepilot of the fastener,and .the entire pilot is then subjected to compression stress. If arelatively large clearance has beenused between the periphery of. thepilot and the shear edge of the die the rest of the compressive stresswill be dissipated in expanding the pilot into, the clear- 1 pierced inthe sheet materiahto result in a frictional hold rather than amechanical interlock. Ariother difficulty is that if the die clearanceistaken .at its maximajority of instances, there is no interlock at all,the 1 pilot merely expanding or upset-ting in theopening.

mum, or if the stroke of the tool pushing the pilot through the materialis not carefully controlled, the fastener may expand and lodge withinthe die. There is thus little or no residual space into which the volumeof deformed material may flow. Yet another difficulty inherent in thismethod is that the slugs or pieces of sheet metal cut out by thepilot asit passes through the sheet will tend to lodge or pile up'between thestep in the back-updie and the. pilot of the fastener.

It is an object of this invention to provide an interlock between aflanged fastener and a sheet of material by expanding selected areas ofthe pilotof the fastenerand cold welding to said expanded areas materialof the,

sheet adjacent thereto to form a strong interlock.

It is also an object of this invention to provide a joint: between arelatively thin sheet materialand a relatively thick material passingthrough said thin sheet material,

said joint comprising an abutment on the thick material on one side ofsaid'thin material and an abutment on the other side of the thinmaterial, the latter being formed by material from both the thick andthin materials cold welded together.

These and other objects of this invention will become apparent from thefollowing detailed description of a preferred form of the invention whentaken together with the accompanying drawings in which:

FIG. 1 is an exploded plan view in perspective of a fastener and diemade in. accordance with this invention, the fastener performing thefunction of a punch FIG. 8' is' a fragmentary plan view of the die ofFIG.

1; v:. i IGS.,9 and 10 are elevations in section of the die of FIG. 8,the sections being taken along lines 9-9 and 10-l0, respectively, ofFIG. 8; 1

. FIGS. 11, 12, 13 and 14 are sections'in elevation of the die similarto FIG. 10, showing the progressive steps in theformation of theassembled fastener and sheet;

FIG. 15 is a bottom view of the assembled fastener and sheet; and

FIGS. 16, 17 and 18 arerespectively plan, side and plan views ofmodifications of the fastener of FIG. 1.

The invention in general comprises forming the fastener with a lateralabutment which may take the form of a flange extending partly orentirely around the fastener, depending upon the configuration of thefastener. An axially adjacent part of the fastener which does not havethe flange is used as a pilot to be brought downagainst and through thesheet material to which the fastener is to be secured. A back-up dieunder the material has an opening to receive the pilot, the openinghaving a configurationcorresponding to that of the pilot except forsmall areas which extend into the opening in the path of the pilot. Theupper portions of these areasare relieved to form steps having concave,semispherical or dimple-like upper surfaces. The inner edges of thesesurfaces form gouges which displace the metal in the sides of the pilot.This displaced metal moves down and laterally outward from the pilotalong the concave surfaces taking with it adjacent portions of thematerial of the sheet, which adjacent portions become welded to it andserve to increase the size and strength of the displaced metal.

Referring now to the drawings for a detailed description of thepreferred embodiment depicted therein, there is disclosed in FIGS. 2 and3 a nut which has been secured to a section of sheet metal 11 by themethod of this invention. As shown in FIG. 1, nut 10, for purposes ofillustration, has a rectangular section at the upper end of which areformed a pair of oppositely disposed laterally extending flanges 12 and13. It is understood that nut 10 may have any number of sides, and itmay in fact be a cylinder, but in the form selected to illustrate thisinvention. nut 10 has four sides 14, 15, I6 and 17, and flanges 12 and13 extend laterally from opposite sides 14 and 16. Nut 10 is formed witha threaded opening 18 adapted to receive an externally threaded fastenersuch as a bolt or screw.

It is contemplated that nut 10 will be non-rotatively secured to sheet11, said sheet being of metal and comprising a panel or wall of astructure, receptacle or the like. Thus, nut 10 is received in anopening 19 formed in sheet material 11 by the nut itself in a piercingoperation hereinafter to be described in detail. Nut 10 therefore fitssnugly in opening 19 and is held against rotation relative to sheet 11.It is also restrained against moving out of opening 19 by deformations20 in both the nut and sheet, said deformations, in accordance with thisinvention, being formed with a single stroke with the aid of a back-updie 21, the deformations being formed on the side of sheet material 11opposite that against which flanges 12 and 13 bear. In the form of theinvention selected for illustrative purposes herein, the deformations 20are disposed at the corners ofthe nut, and take the form, in plan view,ofsomewhat frusto-spherical bosses scooped or gouged out of the cornersto leave concave, arcuate grooves 22, 23, 24 and 25 in said corners. Asshown in FIGS. 4-7 inclusive, each of the bosses is comprised ofmaterial 26 originating in nut 10 and material 27 originating in sheetmaterial 11. As shown more clearly in FIG. 7, the material 26 from nut10 and the material 27 from sheet material 11 is compressed together inan axial direction in a manner to bond the two together to make asubstantially integral boss 20 the outer surface of which has theaforesaid frusto-spherical shape.

It may be apparent from the description thus far given that bosses 20and flanges 12 and 13 clinch sheet material 11 between them to hold nut10 against axial movement out of opening 19 in sheet material 11. Thusthe plane of the frustum which defines the base of the bosssubstantially coincides with the surface of the panel adjacent the boss.

Referring now to FIGS. 8, 9 and 10, back-up die 21 has an opening 28which is of the same configuration as the portion of nut 10 belowflanges l2 and 13, and of a depth sufficient to give the die thenecessary strength to resist deformation under the shear stressesrequired to pierce sheet material 11. It has been found that a depthequal to approximately five thicknesses of sheet material 11 issufficient for this purpose. Die 21 has an enlarged opening 29immediately below opening 28 to receive the material punched out ofsheet 11 by nut 10. Circular depressions 30 are formed in the corners ofopening 28, said die 21 having inwardly extending steps 31 at eachcorner generally completing the circular profile of the depressions 30.

The surface 32 of each depression 30 is concave frustospherical ordimple-like and terminates in a somewhat rounded edge 33 where surface32 intersects the surface of the inwardly projecting steps 31. Thedeformations or bosses 20 are formed in the circular depressions 30 inthe following manner:

Referring to FIGS. 11-14, back-up die 21 is shown with the sheetmaterial 11 placed thereon and with a nut 10 placed over sheet 11 inaxial alignment with the opening 28 in die 21. The view in FIGS. 11-14is taken along a diagonal across the opening 28 and is the same view asin FIG. 10. Nut 10 is intended to form its own opening in sheet material11 and to that end, it is only necessary that the edges 34 at the bottomof nut 10 and forming collectively the periphery of said nut at sheet11, be reasonably sharp and that the sides 14, l5, l6 and 17 of the nutbe parallel with the axis of the nut or perpendicular to the uppersurface 35 of sheet material 11. It is assumed in the stage shown inFIG. 11 that several nuts have been previously applied to sheet material11 with the aid of die 21 so that opening 28 has a number of slugs 36frictionally retained therein, each slug having been progressivelypushed downwardly through opening 28 by the next succeeding slug.

The first stage in the movement of nut 10 into opening 28 in die 21 isshown in FIG. 12. In this stage, the edges 34 of nut 10, acting as shearedges, have partially sheared a slug 37 from sheet 11, the portions ofsheet 11 over circular depressions 30 however being merely displacedaxially downwardly into said depressions 30. At the stage shown in FIG.12, slug 37 is in contact at its corners with the rounded edge 33 at theinner ends of steps 31.

The next stage in the movement of nut 10 into opening 28 is shown inFIG. 13, and at this stage the bottom surface 38 of nut 10 has contactedthe rounded edges 33 and the material of sheet 10 which was disposedover depressions 30 has been displaced downwardly and laterallyoutwardly into said depressions 30.

The amount of material from sheet 11 displaced into the depressions 30,however, is not sufficient to fill said depressions so that only themajor part of the boss has the frusto-spherical shape. It may be notedthat the completed slug 37 has now pushed a preceding slug 36 into theclearance opening 29 and that the lowermost slug 36 is substantiallyhalf way out of the opening 28.

The final stage in the movement of nut 10 into opening 28 is shown inFIG. 14. In this stage, the edges 33 at the inner ends of concavesurfaces 32 have now cut into the corners of bottom surface 38 on nut 10and, because of the concave nature of said surfaces 32, the material inthe corners of nut 10 has been displaced laterally outwardly against thepreviously displaced material of sheet 11 in these depressions 30 tocontinue the movement of said displacement sheet material into thedepressions 30. It may be noted that even at the bottom of the stroke ofnut 10, the depressions 30 still are not completely filled, so thatthere is no binding effect created between the nut and die by virtue ofthe displaced material. The material of sheet 11 displaced by nut 10into depressions 30 is shown at 39 in FIGS. 13 and 14 and the materialof nut 10 displaced by the die is shown at 40 in FIG. 14. As shown inFIG. 13, the material from the nut is forced upon concave surface 32 andcompressed against and partly under the previously dis- .placed material39 from sheet 11. The pressure is sufficient to form an integral boss 20wherein the material from both the nut and the sheet have, in effect,been cold welded together. The movement of nut to its final stage inopening 28 has caused the lowermost plug 36 to be ejected into theclearance space 29 in die 21. Sheet 11 may now be lifted off die 21, andnut 10 will be firmly clinched upon sheet 11 by the flanges 12 and 13 onthe one side and the bosses on the other.

Since nut 10 acts as a punch to shear slugs 36 from sheet 11, it must beof sufficient thickness to withstand the compressive force exertedthereupon during the piercing operation without exceeding its maximumcompression strength. I

Depressions 30 are shown generally circular in outline. They may haveany other shape desired, the circular form being the simplest and mosteconomical to make. Similarly, the inwardly projecting steps 31 need notbe a continuation of the contour of the depressions 30 but they needonly to be so related to the depressions that the volume of materialdisplaced from the sheet 11 and nut 10 will not exceed the volume of thespace in said depression 30.

Opening 28 in die 21 and the inwardly projecting steps 31 can readily beformed in a single operation by the use of a broach. Depressions 30 canbe formed equally as readily with the use of an appropriately shaped endmill.

It may be noted in FIG. 12 that nut 10 has moved approximately one-halfthe thickness of material 11 toward die 21, and it may be taken as oneof the criteria for the design of the die 21 that in the FIG. 12 stagethe nut will move one-half the thickness of the material toward die 21so that the material 11 will be definitely sheared by the die 21 aroundthe periphery of the opening between depressions 30. At the depressions,however, the material disposed above said depressions is extruded,rather than sheared, so that whatever material enters the depressions isstill a part of sheet 1 1. The ductility of the material of sheet 11,however, will have some effect upon the location of the end of the shearand the commencement of the extrusion of the material. Generally, thiscommencement of the extrusion process will occur where the straight edgeof the opening 28 intersects the rounded edge 33, but it is possiblethat once shear has been propagated in a very brittle sheet material, itmay well continue along the shear edge into the depressions 30 where itterminates against the shear propagated at right angles from theadjacent edge. However, complete shearing of the material in depressions30 will not affect the successful formation of the bosses 20, since thecompressive stresses imposed upon the material in the bosses causes thematerial to reunite with the sheet at the end of the stroke of nut 10.

Although a line of demarcation has been shown in the drawings betweenthe material of the sheet 11 and the material of nut 10 in depressions30, actually, in the final structure, this line cannot be seen, sincethe two materials have been compressed together by the die and nut andhave become bonded together.

Thus by a single stroke ofa punch, nut 10 has pierced an opening insheet 11 and has been clinched to the sheet on both sides of theopening. A stronger clinching action has been achieved so that the nutwill resist a greater axial pull while at the same time avoiding anybinding effect of the clinched nut in the back-up die.

FIG. 16 shows the method of this invention applied to a hexagonal nut41. In this case, a continuous flange 42 (shown dotted) may be usedwhere maximum strength is desired. The bosses formed by this method areshown at 43, said bosses being six in number corresponding to the sixcorners available in a hexagonal nut. The back-up die (not shown) bywhich bosses 43 are formed is made in accordance with the principles setforth in connection with die 21.

In FIG. 18 is shown a threaded cylindrical fastener 44 which has alsobeen applied to a sheet 45 by the method of this invention. In thiscase, a continuous flange 46 (shown dotted) may also be used, and thenumber of bosses 47 may be selected to provide the necessary resistanceto removal from the opening punched in sheet 45 by the fastener 44. Itis preferred that whatever number of bosses be selected, they beequidistantly spaced from one another to provide uniform strength andresistance against removal of the sleeve from the sheet 45.

Since the threaded opening in any of the abovementioned fasteners 10, 41and 44 is not utilized in the process of this invention, it may beapparent that the said process may be used to secure the heads of screwsor bolts to a sheet or panel, or to secure pins or shafts to a panelwhen such pins or shafts are provided with an appropriate head.

Thus it is understood that this invention is not limited in its scope tothe structure hereinabove described, but its scope is to be determinedinstead by the appended claims.

I claim:

1. A sheet metal panel and a metal part of greater thickness than thesheet metal panel rigidly secured to said panel, said metal part havinga bore and an abutment overlying one side of said panel, said metal partextending through said panel, and said panel and metal part havingoverlapping portions thereof extending laterally of the metal part onthe other side of said panel, said overlapping portions togetherconstituting for the major part adjacent the metal part a boss having anexterior surface in the form of a frusto-sphere the plane of the frustumsubstantially coinciding with the surface of the panel adjacent saidmetal part 2. The combination disclosed in claim 1, said metal partcomprising a polygonal nut having intersecting sides to form corners andhaving further a second abutment diametrically opposite the first saidabutment,

and there being a boss disposed at each of the corners of said polygonalnut.

3. A sheet metal panel and a metal part of greater thickness than thesheet metal panel rigidly secured to said panel, said metal part havinga bore and an abutment overlying one side of said panel, and said paneland metal part having overlapping portions thereof extending laterallyof the metal part on the other side of said panel, said overlappingportions of the panel and metal part being united to form an integralboss the major part of which adjacent the metal part has afrusto-spherical surface the plane of the frustum of which substantialycoincides with the surface of the panel adjacent said metal part.

1. A sheet metal panel and a metal part of greater thickness than thesheet metal panel rigidly secured to said panel, said metal part havinga bore and an abutment overlying one side of said panel, said metal partextending through said panel, and said panel and metal part havingoverlapping portions thereof extending laterally of the metal part onthe other side of said panel, said overlapping portions togetherconstituting for the major part adjacent the metal part a boss having anexterior surface in the form of a frusto-sphere the plane of the frustumsubstantially coinciding with the surface of the panel adjacent saidmetal part
 2. The combination disclosed in claim 1, said metal partcomprising a polygonal nut having intersecting sides to form corners andhaving further a second abutment diametrically opposite the first saidabutment, and there being a boss disposed at each of the corners of saidpolygonal nut.
 3. A sheet metal panel and a metal part of greaterthickness than the sheet metal panel rigidly secured to said panel, saidmetal part having a bore and an abutment overlying one side of saidpanel, and said panel and metal part having overlapping portions thereofextending laterally of the metal part on the other side of said panel,said overlapping portions of the panel and metal part being united toform an integral boss the major part of which adjacent the metal parthas a frusto-spherical surface the plane of the frustum of whichsubstantialy coincides with the surface of the panel adjacent said metalpart.